I had this once, combination problem.
The idle switch behind the a/f sensor in the linkage was bent and with closed throttle the CIS-E control unit had no idea the car was closed throttle. The same car has a freeze plug in the inke that had rotted to lower section out and was sucking air along with a line under the a/f sensor housing that was busted.
Dunno if it'll help but I'll damn sure remeber that one. At least it was my car so it wasn't a issue.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.